Natural gas and small amount of condensates were obtained in Rub Al Khali Basin.The Ordovi cian condensates from well A2,with carbon isotopic value from-26.55％0 to 27.70％‰,was dominated by the alkanes with carbon numbers smaller than 17.The condensates has high saturated fraction with no as phaltene.The content order of group composition is as follows:saturated fraction ＞ aromatic fraction＞ non hydrocarbon fraction.The heptane and isoheptane values of the condensates are 22 ％ and 2.38,respec tively.The biomarker contents of the condensate are low,with hopane dominating in the terpanes and C23 tricyclic terpane dominating in tricyclic terpane,and low content of C24 tetracylic terpane.The condensates have high content of diasterane,with regular sterane distribution being C29 ≈C27 ＞C28.The biomarker dis tribution of the Ordovician condensates is similar to that of the Paleozoic oils sourced from Silurian hot shale.The maturity parameters of biomarker and diamondoids suggest the condensates to be mature to high mature.All the natural gases from different time in Block B are wet gas of organic origin.The maturity of these gases ranges from 0.75％ to 1.35％.Due to the similar maturity between the condensate and natural gas,it is suggested that the oil cracking may not be the only gas origin.Condensates and natural gas may be mainly sourced from the thermal cracking of Silurian hot shale.
CondensatesNatural gasGeochemistryBlock B in Saudi ArabiaPaleozoicRub Al Khali Basin
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万方数据
